1. Field of the Invention
The present invention relates to a holding construction for holding an optical component of an optical system for use in a liquid projector and a DLP projector. The present invention relates more particularly to a holding construction for holding a rod integrator that provides uniform distribution of brightness in an image plane, and to a video image-displaying apparatus that employs such a holding construction.
2. Description of the Related Art
FIG. 15 illustrates a prior art rod integrator disclosed in Laid-open Japanese Patent (KOKAI) No. 11-326727.
FIGS. 16A-16C illustrate the prior art rod integrator held by a holding member.
A rod integrator 1 has a reflecting side surface 2. If the reflecting side surface 2 is in contact with a light-absorbing material, the intensity of the light reflected from the side surface 2 decreases. In order to prevent this problem, aluminum reflective layers 101 are deposited at two locations on the reflecting side surface 2, the two locations being spaced apart from each other in a longitudinal direction of the side surface 2.
A holding member 103 has two contact surfaces 102 that are connected to the reflecting side surface 102 by an adhesive 104. The contact surface 102 is smaller in area than the reflective layer 101. As shown in FIG. 16B, the adhesive 104 is also applied to the holding member 103 and the reflecting layer 101 to surround the holding member 103, so that the holding member 103 is firmly connected to the rod integrator 1. This construction reduces non-uniform illuminance of light exiting the rod integrator 1.
The aforementioned conventional construction requires more number of manufacturing stages because an aluminum layer needs to be deposited on a part of the side surface 2 of the rod integrator 1. Thus, the aforementioned conventional construction is costly. In addition, when the rod integrator 1 is mounted to the holding member 103, the holding member 103 may be inadvertently mounted to a side opposite to a side on which the aluminum is vapor-deposited. Thus, the aforementioned prior art suffers from poor assembly efficiency. Moreover, the adhesive is subjected to increases and decreases in temperature within the video-displaying apparatus, loosing adhesion gradually. Deterioration of the adhesive may cause the rod integrator 1 to drop from the holding member 103 when the assembly is subjected to vibration and/or impact. Thus, bonding is not reliable. If the rod integrator 1 is to have a larger area in contact with the holding member 103 for enhanced reliable bonding effect, then the aluminum must be vapor-deposited to a larger area on the rod integrator. However, the reflection by the vapor-deposited aluminum is less efficient than the total reflection in the glass material. As a result, increasing an area of the rod integrator 1 in contact with the holding member 103 decreases the amount of light exiting the rod integrator 1.
The present invention was made in view of the aforementioned problems.
An object of the invention is to provide a reliable holding means for holding a rod integrator.
A video-displaying apparatus uses a rod integrator that converts light emitted from a light source into uniform light. The apparatus comprises a rod integrator, a holding member, and a flat spring. The rod integrator has a first surface and a second surface that opposes the first surface. The holding member has a first contact surface to which the second surface abuts. The first contact surface has a smaller area than the second surface. The flat spring has at least one spherical projection. The rod integrator is fixedly mounted to the holding member such that the rod integrator is sandwiched between the holding member and the flat spring mounted to the holding member. Only the projection abuts the first surface of the rod integrator.
The rod integrator further includes a third surface and a fourth surface that opposes the third surface. The at least one projection may be one of a plurality of projections. The holding member further includes a second contact surface having a smaller area than the fourth surface. The fourth surface abuts the second contact surface and only the projections abut the first surface and the third surface of the rod integrator.
The holding member is an assembly separate from a base on which optical components are mounted. The rod integrator includes an incidence surface and an exiting surface that have the same aspect ratio as a video image incident on the rod integrator. The holding member is positioned such that an optical axis of the rod integrator is at a predetermined position regardless of the aspect ratio. The spring has at least one elongated hole that extends in a direction substantially perpendicular to the optical axis of the rod integrator.
The base comprises a chamber in which the rod integrator is housed such that light incident on the rod integrator passes through the chamber. The holding member has a first wall and the base has a second wall such that the first wall and second wall are arranged side by side to define a part of the chamber and a gap between the first wall and second wall is minimal.
The rod integrator may have a recess formed therein and the recess receives the projection.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.